Digital audio is the foundation of sound on computers and the web. Sound itself is a vibration that travels as a wave through the air, and when you listen to music or any audio, you are actually hearing these pressure changes. The basic characteristics of a sound wave are its frequency—which determines the pitch—and its amplitude—which determines the loudness.

• Frequency is measured in hertz (Hz) and tells you how many times the wave repeats per second;
• Higher frequencies sound higher in pitch, while lower frequencies sound lower;
• Amplitude represents the strength or height of the wave; greater amplitude means a louder sound.

When sound is captured and stored on a computer, it must be converted from its continuous, analog form into a digital format. This process is called digital representation. The sound wave is sampled at regular intervals (the sample rate), and each sample records the amplitude at that moment. The result is a stream of numbers that the computer can process, store, and play back.

The Web Audio API is a powerful interface that allows you to generate, process, and control audio entirely within your web applications. At the heart of the Web Audio API is the concept of nodes. Each node represents an audio processing module, such as a sound source, effect, or destination (like your speakers). You create and connect these nodes to form an audio graph, which defines how sound flows and is transformed.

The AudioContext is the central object that manages everything in the Web Audio API. When you want to work with audio, you create an AudioContext. This context is responsible for controlling the timing and flow of audio signals through the nodes you set up. You can think of it as the conductor of an orchestra, coordinating all the different instruments (nodes) and making sure they play together in sync.

Signal flow in the Web Audio API is all about connecting nodes in a chain or network:

• Connect an oscillator node (which generates a tone) to a gain node (which controls volume);
• Connect the gain node to the destination node (your speakers).

This modular approach makes it easy to build complex audio effects and instruments right in the browser.